Locking devices for electrical plugs as are used on electrical cords for appliances, tools, motors and other electrically driven devices, are old. Illustrative prior art includes Katy U.S. Pat. No. 2,654,073 wherein a spring-loaded detent is reciprocated by a key-operated barrel which engages the detent through a cam arrangement. Other art discloses different shapes of bolt heads and slotted screw heads for use with shaped wrenches and screw drivers.